Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described and claimed herein.
Auscultation of the lung and heart is probably the most widely used physical diagnostic method in respiratory and cardiac disease. However, due to the limitations of the human auditory system, auscultation has such low sensitivity and specificity that many physicians no longer rely solely on it as a diagnostic tool. Although digital acquisition and analysis of physiologic sounds has the potential to be of tremendous diagnostic/therapeutic benefit to patients, the medical community has been slow to embrace this technology. In order to overcome this obstacle, any system for digital acquisition and analysis of physiologic sounds must be lightweight and easy for individuals without technical expertise to operate and modify. In addition, all generated results must be presented in a format that allows for rapid interpretation and correlation with important physiologic values obtained from other tests. A description of the prior art and their perceived shortcoming relevant to the objectives of the present invention follows herein.
Physiologic sounds may be captured electronically, processed, and transmitted back to the clinician thus enabling the human auditory system to obtain greater information conveyed by the signal. For example, U.S. Pat. No. 5,774,563 discloses a device for acquiring physiologic sounds. Electronic circuitry embedded in the device enables the operator to filter and amplify the incoming signal. Furthermore, this device also allows the user to listen to the post-processed signal through implementation of earpieces. However, no plan is described for enabling clinicians of ordinary ability to modify the system. Thus, the effective frequency range measured by this device is 70-480 Hz, which is essentially unalterable, has minimal clinical applications. In addition, this system does not provide a means for digital acquisition/display/analysis of the recorded signal, which serves to severely limit the use of this device in a clinical setting. Other forms of analogous art, which are based on these same principles, share similar disadvantages.
Analogous inventions in the art have depicted devices capable of acquiring, processing and digitally recording/analyzing physiologic signals. U.S. Pat. No. 6,139,505 discloses an electronic stethoscope for the digital acquisition and analysis of physiologic sounds. The device consists of a microphone, which can be embedded inside conventional chest pieces. After amplification and filtering, the signal is transferred to an analogue to digital converter (A/D converter) for computer analysis. The system disclosed contains a modifiable number of independent transducers to record physiologic sounds at any particular location, which the operator desires. The device allows for amplification/filtering of the recorded signal, store these recordings in memory, perform root mean square (RMS) and time expanded waveform analysis, and display data on a monitor for visual analysis/printing. This device is also fairly easy to modify/upgrade/repair and includes a built in program for analyzing respiratory sounds and generating a probable diagnosis based on this information.
However, this device does not disclose a method to enable the physicians to listen to the sound as it is being recorded, but instead, requires them to discern phases of the respiratory cycle simply by inspection of the time expanded waveform. The patent describes a method by which physiologic sound may be processed and transmitted to a computer workstation using analogue circuitry which is bulky and not easily customized thus limiting the device's practical application. Further, no information is given about how this device can be used for higher level analysis (such as performance of Fourier Transformation or wavelet) of the desired signal, only time expanded waveform analysis and RMS of the complete spectrum are illustrated. These quantities give incomplete information regarding the sound and the program is not easily operated/modified by a clinician of ordinary skill. Lastly, no method is outlined by the inventors for reducing the corruption of the data from inadvertent pickup of ambient noise or superimposed signals emitted from other organs in close proximity to the transducer. The probable diagnosis product available with this device is also extremely limited since it provides no quantitative information regarding the degree of functionality of the desired organ system. Although Murphy's electronic stethoscope represents significant improvement from analogous art as a system for the display and analysis of physiologic sounds, the limitations of this device as described above decrease its usefulness in a clinical setting.
Additional devices have been patented which attempt to provide more sophisticated means for mathematically analyzing physiologic sounds and transmitting results to remote locations. One such example can be found in U.S. Pat. No. 6,699,204, which illustrates a device for recording physiologic sound using multiple sensors that are secured to a patient via a harness. Physiologic sound can be recorded by the sensors and relayed to a processing station for filtering/amplification using analogue circuits. The signal is then transferred to a sampler Ech (sound card) for digital recording via analogue circuitry or modem (not shown). With the aid of a specialized calculation manager (Matlab® for example), the device can evaluate a set of transformed intensity levels, each associated with a predetermined sound frequency and means for storing each transformed intensity level in correspondence with an associated frequency for the purpose of displaying these intensity levels, transformed on the basis of frequencies as a spectral representation of the auscultation sound.
The device depicted by Kehyayan et al. is a further improvement over analogous art since it provides an accurate spectral representation of the auscultation sound as the intensity varies with time. However, a physician of ordinary ability cannot be expected to have the technical expertise necessary to easily operate and/or modify this analysis program in order to examine a wide array of physiologic sounds. Also, no plan is outlined by the inventor for preventing extraneous sounds (from ambient noise or sound emitted from other organs) from influencing the results displayed on the spectral plots. Lastly, the spectral plots contain too much information for a clinician to interpret in a timely manner. Thus, it is unlikely that the invention proposed by Kehyayan will be useful in a practical setting, and thereby widely embraced by the medical community.